title: Connexin 43 and hearing: possible implications for retrocochlear auditory processing.
abstract: OBJECTIVE
  To examine the relationship between hearing and connexin 43, a dominant gap junctional protein in the central nervous system.
  
  
  METHODS
  Original research.
  
  
  METHODS
  Connexin 43 heterozygous mice are used to assess its mutational effect on hearing. Results are compared to controls consisting of connexin 43, wild type and CBA/J mice. Hearing is assessed using auditory brainstem response and distortion product otoacoustic emissions tests. Distribution of connexin 43 in the organ of Corti and the retrocochlear auditory centers (eight nerve, cochlear nucleus, olivary complex, lateral lemniscus, inferior colliculus, respectively) is examined. Fluorescent markers are used to elucidate cell types.
  
  
  RESULTS
  Mean click auditory brainstem response threshold for the young connexin 43 heterozygous mice (3-4 months) was 36.7 ± 12.6 dB compared to 25 ± 0 dB for control mice (P < 0.05). Mean threshold difference became more pronounced (68 ± 7.5 dB vs. 31 ± 2.2 dB) at 10 months (P < 0.05). Tonal auditory brainstem response testing showed elevated thresholds (>60 dB) at all frequencies (4-32 kHz) compared to the controls. Distortion product otoacoustic emissions (DPOAE) were present in all the mice, although the older connexin 43 heterozygous mice responded at higher thresholds. The pattern of connexin 43 immunoreactivity was distinctive from connexin 26 and 30, showing minimal presence in the organ of Corti but robustly present in the retrocochlear centers.
  
  
  CONCLUSIONS
  Connexin 43 heterozygous mice demonstrated greater degree of hearing loss compared to age-matched controls. It is abundantly found in the retrocochlear auditory centers. The mechanism of hearing loss in these mice does not appear to be related to hair cell loss.
authors.affiliation: Department of Otolaryngology, New York Eye and Ear Infirmary, New York; New York Medical College, Valhalla, New York.
authors.forename: Ana H
authors.initials: AH
authors.lastname: Kim
authors.forename: Edmund
authors.initials: E
authors.lastname: Nahm
authors.forename: Anne
authors.initials: A
authors.lastname: Sollas
authors.forename: Linda
authors.initials: L
authors.lastname: Mattiace
authors.forename: Renato
authors.initials: R
authors.lastname: Rozental
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold / Q000502:physiology; D003051:Cochlea / Q000378:metabolism* / Q000503:physiopathology; D018031:Connexin 43 / Q000502:physiology*; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D006309:Hearing / Q000502:physiology*; D034381:Hearing Loss / Q000378:metabolism* / Q000503:physiopathology; D051379:Mice; D008808:Mice, Inbred CBA; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology
chemical_list: D018031:Connexin 43
keywords: Connexin 43; hearing loss; retrocochlear auditory pathway